1. Field of the Invention
The present invention relates to a powder-projecting type recording apparatus for forming a recording image with a powdered developing agent without forming an electrostatic latent image, particularly to a case of forming a recording image of a plurality of colors.
2. Description of the Related Art
The so-called electrophotographic recording apparatus invented by C. F. Carlson in 1938 has been widely used so far for copying machines, facsimile systems, or printers. The electrophotographic method forms an electrostatic latent image on a photoconductive light-sensitive body. However, the photoconductive light-sensitive body is expensive and a lot of time and expenditure is required to maintain the body. However, Japanese Unexamined Patent Publication JP-A 1-503221(1989) (International Publication WO 89/05231) discloses the prior art for a powder-projecting type recording apparatus capable of directly recording an image on a recording paper by using powdered developing agents without forming an electrostatic latent.
The prior art for the powder projecting method magnetically holds magnetic toner on the surface of a developing roller as developing agents, flies the toner through the electric field control by printing control electrodes set adjacently to the surface of the developing roller, accelerates the toner by applying an acceleration voltage to the printing control electrodes, and making the toner attach onto a recording paper to directly form an image. By performing the electric-field control by the printing control electrode at high accuracy, it is possible to obtain an image with high resolution without forming an electrostatic latent image.
To obtain an image with high resolution by the powder projecting method, high accuracy is required for printing control electrodes. Therefore, a particularly large printing control electrode becomes expensive. Moreover, because a recording member such as a recording paper is inserted between printing control electrodes and a printing acceleration electrode, the projecting states of developing agents are changed due to the thickness of a recording member and thereby, the recording quality of an image may be deteriorated. Furthermore, electrical properties including conductivity of a recording member are changed due to the change of an environment such as humidity and attachment states of a developing agent are changed and thereby, the recording quality of an image is easily deteriorated. Furthermore, because the thickness of a recordable recording member is limited due to the interval between printing control electrodes and a printing acceleration electrode, it is impossible to record an image on a recording member having a thickness exceeding the interval.
These problems are left to powder-projecting type recording arts having been proposed so far as the subjects to be solved. Moreover, the request for easily recording a color image has been intensified.
To obtain an image with high resolution by the powder projecting method, a lot of printing control electrodes 290 are necessary and moreover, it is necessary to increase the density for arrangement on the same flexible printed circuit board (hereafter referred to as "FPC") 291 as shown in FIG. 37. Moreover, the number of driving circuits 294 mounted on a printed circuit board 292 to drive these printing control electrodes 290 at +300 V supplied through a connector 293 increases proportionally to the number of printing control electrodes 290 and many driving circuits 294 are necessary. Because the driving circuit 294 requires a high breakdown voltage because of controlling a high voltage of approx. +300 V, it is impossible to greatly improve the integration degree. Therefore, the cost increases. Therefore, the cost of the driving circuit 294 increases as the resolution rises and thereby, the reliability deteriorates. Furthermore, failure rate of the entire driving circuits 294 increases as the number of the driving circuit 294 increases. Furthermore, a high precision is required of a printing control electrode at high resolution and accordingly the cost increases. Furthermore, in the case of a color image, the number of printing units increases and thus, the cost for the driving circuit 294 further increases.